The present invention relates to a superconductive apparatus such as a superconductive coil, a superconductive motor, a superconductive application element, a superconductive wire, etc. which is used in a neutron existing place as in a high energy particle accelerator, in a nuclear fusion apparatus, in a nuclear reactor, etc. and, more particularly to a superconductive apparatus which is suitable to prevent superconductive material used therein from heat generation and being damaged due to neutron radiation.
A superconductive apparatus concerned with the present invention is used in high energy particle accelerators, in nuclear fusion apparatus, in the nuclear reactors, etc. In such a plant, neutrons are generated, and a lot of neutrons are present in a particular place of the plant.
For example, in a proton accelerator, reactions of atomic nuclei and protons cause an intranuclear cascade, whereby neutrons of high energy are emitted, and neutrons of low energy are emitted from the remaining atomic nuclei in an evaporation process. Therefore, a lot of neutrons are present in a room accommodating the proton accelerator, and in particular, around a beam dump.
In the nuclear fusion apparatus, neutrons having an energy of 14 MeV are generated by reaction of deuterium and tritium in a nuclear fusion plasma. Therefore, a lot of neutrons are present in the nuclear fusion apparatus.
When the superconductive apparatus is used in a place in which a lot of neutrons are present, heat generation by neutron radiation occurs in superconductive material of the superconductive apparatus, so that it is necessary to sufficiently cool the material to keep it below the critical temperature thereof. Therefore, in order to avoid heat generation of the superconductive material by neutron radiation, it is considered to shield neutrons by enclosing the superconductive apparatus with neutron shielding material such as polyethylene. Further, in case of the superconductive coil, for instance, it is disclosed in JP A 61-102710 that the superconductive coil is disposed in a case, and the interior of the case is cooled with liquid helium.
The above-mentioned prior art that encloses the superconductive apparatus with a neutron shielding material such as polyethylene has a problem in that heat generation by secondary gamma rays generated from the neutron shielding material cannot be avoided. Further, the prior art disclosed in the JP A 61-102710 in which the superconductive material is disposed in the casing and the interior of the casing is cooled with liquid helium has a problem in that the cooling apparatus is very large.